Milling



Dec. 5, 1944. A. G. scHURMAN MILLING 5 Sheets-Sheet l Original Filed Nov. 4, 1957 Dec. 5, 1944. A. G. SCHURMAN v 2,364,101

MILLING Original Filed Nov. 4, 1957 5 Sheets-Sheet 2 MILLINC Original Filed Nov. 4, 1957 Sheets-Sheet 4 Summa/1J Dec. 5, 1944. A, scHuRMAN 2,364,101

MILLING original Filed Nov'. '4, 1937 5 sheets-sheet 5 (7j/g. 6. @107% www figg-55g;

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Patented Dec. 5, 1944 Adolph G. Schurman, Baltimore, Md.

Original application November 4, 1937, Serial No. 172,815. Divided andthis application August 12, 1941, Serial No. 406,539

9 Claims. (Cl. 83-94) This invention relates to milling and more particularly to the grinding and separationof ma terial to be milled into finely powdered material.

This application is a division of my copending application Serial Number 172,815, filed November 4, 1937.

Prior to the instant invention, in the manufacture of finely powdered material, considerable trouble and loss of capacity or inefficiency has been experienced by the inability to remove the finished material from the grinding chamber rapidly enough to prevent the fine material from acting as a cushion so that the full force of at a uniform rate the finished product would not be of uniform quality. These diiiiculties, too, have been overcome by applcants invention which operates rapidly, continuously and uniformly.

It is an object of the instant invention to teach a novel method of effecting high milling eiciency and efficient separation of the finished product.

It is a further object of the instant invention to provide a novel method of milling.

Otherobjects and the nature and advantages l of the invention will be apparent from the followin'g description taken in conjunction with the accompanying drawings, wherein:

Figure 1 is a side elevation of a mill assembly in accordance with the invention;

Fig. 2 is a top plan View of a portion of the assembly illustrated in Fig. 1;

tion contemplates passing the materialdirectly f into a pulverizing area in a continuous stream where it is acted on by grinding elements while passing through the pulverizing area. On leaving this pulverizing area, the entire stream of material is swept out of the grinding chamber with a current of air and the fines are removed only after the pulverized material has beenso swept out.

Prior attempts at handling large quantities of pulverized materials have been relatively unsuccessful because it has been found impractical to efficiently separate the fines from the bulk of the material to be pulverized. To overcome this diffculty a new type of separator has been provided in accordance With the invention to handle the relatively great bulk of material in a continuous stream and at a very high velocity. In those cases in which a Very line, high quality finished material is desired, it has been found desirable, in accordance with thel instant invention, to uti-- lize a second separation. step to further refine the finished product. Further, in accordance with the instant invention, provision has been' made for the return of coarse Amaterials from each of the separators or from each of the separation steps to the pulverized area in a uniform, continuous stream. It has been found that in the grinding of some materials, the coarse constituents leading from the separators or separation steps is of different quality from the whole material and that if the vcoarse material from the separators or separation steps were not returned Fig. 3 is a vertical sectional View taken along line 3 3 of Fig. 4, depicting the grinding chamber and related parts;

Fig. 4 is a vertical sectional view taken along the line 4 4 of Fig. 3;

Fig. 5 is a view in elevation of the separator incorporated in the mill assembly depicted in Figure 1;

Fig. 6 is a vertical sectional view with parts shown in elevation and parts broken away, the sectional portion taken alongvline A-A on Fig. 5 and looking in thefdirection of the arrows;

Fig. 'l is a top plan view of the separator shown in Fig. 5; i

Fig. 8 is a vertical sectional View taken along line B-B of Fig. 7 and looking in the direction of the arrows.

Referring to the drawings, the reference letter A designates a base on which the beams I rest and support the mill to be described in detail later. The lower section 2 of one part of the mill structure may be secured to the beams l in any suitable manner, and the second and third sections of the mill, 3 and 4, respectively, are mounted on the section 2, said sections being suitably secured to each other by any suitable means such as the bolted angle irons 5, for example.

Within the sections 2 and 3, the discs 6 are 'mounted on the suitably supported rotatable will be hereinafter referred to, and the said discs are connected adjacent their respective perip-heries by means of the rods l to which are secured the beaters l2 in a manner so that they rotate with the discs 6 and the shaft 1, which is driven by the motor M.

Surrounding the discs 6 and the beaters I2 is a casing I3 within which is a wall composed of a number of segments I6. The inner peripheral faces of said segments may be composed of toothlike projections I'I, though they may be of any desired shape. These projections I1 cooperate with the beaters I2 to grind the material within the mill into a fine powder. At both sides of. the

segments IE, see Fig. 3, a ller I4 is located, the

inner peripheral faces of which are beveled as at I5 and have straight vertical sections as at I5r'LL These continuous inner peripheral faces I5 and |511 and the tooth-like projections I1, in cooperation with the closely spaced beaters I2, form a path between the inlet 29 and the outlet at the bottom of chute 20, see Fig. 4, for the material to be ground.

The air ports I and the discs 6 allow some of the air entering the grinding chamber through pipes 44 to flow through the discs 6 in order that air passing between the beaters I2 at I2a into the chute 20 will be uniform over the entire width of the outlet. e

Wedgcfshaped filler Id, see Fig. 4, is in the same plane at I5g `as the element I5a, but tapers to an edge at lh to provide `a smooth entrance for incoming material to be ground and cause all the material to fall directly on the beaters I2. Wedge-shaped filler I 5c is in the same plane as the element I5 a at I5e and tapers to an`edge at I5f to provide a smooth entrance to the chute 20. Element I5b is in the same plane as element I5a and acts as a filler to make the inner peripheral faces substantially continuous,

One side of the casing ,3 is provided with a doorway I8 and door I9, to which is secured a baiiie Isa, the door and baiile being so constructed and related that they may be readily removed.

The chute 20 is positioned near one Wall of the casings 3 and 4 and opens at its lower end into the compartment I2a housing the discs 6 and beaters I2. The lower end of one wall of the chute 2U is formed by the baiiie I9a, see Fig. 4. The opposite Wall 23a of the chute 2l) extends downto the tips of the beaters I2 and acts as a baiile to 'guide material and air into chute 2l).

The chute 20 extends upwardly and continues to the topof the casing or jacket 4, and then curves inwardly, as at 20a, toward the center of the casing or jacket 4, and then the chute 23 extends downwardly as at 2|. A vane 24 may 'be pivotally mounted to the lower end of the chute wall 23 and vanes 25 may be pivotally mounted to the lower end of the chute wall 22. The vanes 25 are So constructed as to form a substantially solid partition when closed, the purpose of which will be hereinafterl explained. As illus.- trated in Fig. 4, the chute 20 discharges into the separating chamber B.

Extending upwardly from the chamber B is an exit chute 21 providedl` at its bottom, at 4one side thereof,'with a pivoted vane 28, which vane in cooperation with the wall 31, acts as an air control.

An inlet chute 29 is in communication with the grinding chamber, in which the discs 6 and beaters I2 are positioned, said chute having therein a rotor 30 composed of a plurality of vanes over which material delivered by worm 4|! and chute 36 iiows through chute 29 to the grinding chamber and beaters. Rotor 30 is provided in the organization in order to block air from entering chute 219 'sind to prevent the interchange of air between chutes 29 and 36 and chute 3|, while permitting material to be ground which has been stripped of air to flow downwardly into the grind ing chamber. Above the rotor 30 an inlet chute 3| is provided in which are slidably mounted a plurality of regulating plates 32 having elongated slots and thumb screws 3334, whereby said plates may be fixed in adjusted positions so that material fed by the worm 40 is evenly and in the desired quantities fed over the entire width `of the mill or grinding chamber. An inlet chute I 36 leading from the chamber B into the chute 20 and separating chamber B travels at very high velocity in order to effect the desired Separation.

'The coarse material is thrown down into the channel 36 and returned to the grinding cha-r11n ber, while the iine material and air passes up wardly through the chute 21, It is t0 be noted that plate 31 forms one wall of the .chamber B. The vanes 24, 2.5 and Z8 are designed to be oper ated manually by the levers 38 to the desired adjusted position.

A suitable conveyor tube 39 extends into the casing 4, and within this tube is a conveyor Screw 0r worm 49 which is preferably, although not necessarily. .0f two diameters, the larger dpiameter extending a predetermined distance Afrom the outer end of the worm, said worm being positioned in-a trough 39a within the casing. This worm feeds material onto the plates 32 from which it passes into the chutes 2 9 and 3I. The shaft `4I of the worm 40 is provided at one end with a sprocket wheel 4Ia on which is mounted a drive chain 42, said chain being also mounted on a sprocket Mb which is fixed to the shaft 4:3

of the vaned rotor 43a. On the opposite end of the shaft 4I is a sprocket 49a which in coopera.- tion with the chain 4022 and sprocket 40e drives shaft 30e of rotor 30. Shaft 4I is driven through sprocket 4Ic preferably from a source which has a variable speed.

The upper ends of the down draft pipes 44 open into the `casing between the vanes 25 and partitions 35, while their lower ends open into the grinding chamber, as indicated in Fig. 4. These ducts are each provided with vanes, or valves 45 which have an operating arm 46 and may be ,set in any adjusted position. Air inlet openings 41 are provided in the ducts 44 which are controlled by their covers 43 which in turn are ,adapted to be fixed in adjusted positions.

The chamber yD is formed below the upper bend of the chute 2n in which is journaled the shaft 49 on which is mounted the air control 5.0 which may be operated and adjusted from the outside by means of the shaft 49 and held in ad? justed position by the set screw 49a, This cham. ber D is in communication with the return air duct 52 leading from the cyclone 5 3. A part, or all, as desired, of the air from the chamber `D passes through either the ducts 44, or vanes 25, the flow of air through either of the ducts 44 be ing controlled by the valves 45.

Valve 5l! may be moved to closed position by operating rod 49, thereby completely closing the opening. into the pipe 52, then all the air'taken in will enter through inlets l1- In'addition, valve 50 may be opened and air inlets 41 closed whereby no air will be taken in and the mill operated as a closed unit continuously recirculating the same air.

The construction of the rotor 30 and the casing around it is such that air is blocked from passing between the grinding chamber, separating chamber, and the feeder. The rotor 30 is composed of a series of vanes, which'in cooperation with the curved sections thereabout, forman air lock in the grinding chamber inlet for stripping the materialpassing through the air lock of air. Each curved section fits closely about the outer edge of the individual vanes and the arc of each section i`s of sufficient length to close the space between the tips of any two vanes, so that no air willpass regardless of the position of the vanes. The construction described involves the cooperation of two vanes with a curved section to form an air lock pocket which prevents air from accompanying material from the feeder or the separator into the grinding chamber.

Material to be pulverized enters Vthrough bin 40:1: and is carried by screw 4I `over plates 32 which are adjusted to distribute the material uniformly over the entire width of inlet 3l onto the rotor 30, which turns counter-clockwise as Viewed in Fig. 4. As the rotor 30 turns, coarse material from chamber B coming clown chute 36 is mixed with fresh material already in rotor 30, then the mixture is passed into inlet 29 directly on to the rapidly revolving beaters, which carry it into the beating area formed by lining segments I6 and revolving beaters I2. The material follows this fore it can rebound `far enough to get behind the head of the beaters in the space I2b, it will be hit by another beater and driven back against the projections I1, consequently the material will have to follow the beating area formed by the projections I1 and the rapidly revolving beaters. The faces Ita keep the material in this beating area from moving sidewise and escaping from between the beaters. The fact that the material is crowded into this beating area tends to crowd out the air so that the material cannot become suspended in the air.

Air coming down pipes 44 enters the grinding chamber and is uniformly distributed between the discs as well as on each side of the rotor. Due to the close spacing of the beaters in relation to each other, air between the members I4 moves with the beaters and will not to any great extent form eddy currents at their trailing edges, which would tend to carry the material being ground outof the beating area formed by the projections I1 and therevolving beaters I2, into the space I2b. f

Should the material enter the space I2b, the beaters could not satisfactorily act thereon for the material would be suspended in the air therein. When the beaters are too widely spaced or the material is moved through the grinding chamber by the air so as to suspend the material in the air, then as the beaters-revolve the material ,is blpwnl from in between them by the,

air before they can appreciably act upon the particles of material being ground.

Baffie 23a extends to the tip of beaters I2 so that material leaving Vthe beaters is guided up into chute 2G. l The beaters I2 throw the material off at a tangent directly into the chute 20; the air fiowing outwardly between the beaters I2 at I2a, assists in carrying the material up into chute 20 and both the material and the air move upwardly through the chute 2li and then intothe separating chamber B. It is to be noted that no movement of air or material upwardly through chute 29 can take place because of the air lock rotor 30. The air has a denite path through pipes 44 into the grinding chamber and out through the beaters l2 at I2a; while the material has an independent path between the projections I1 and the beaters I2. However, both the ground material and air discharge intoa common outlet.

The ground material and air moving up chute 2D and around the curve 20a are separated into indistinct layers, by the action rof centrifugal force, with the coarse material at the outermost circumference and the air at the innermost circumference. The ground -material and air are then thrown into separating chamber B, past vane 24 which is set at such an angle so as not to disturb the indistinct layers of ground material and air. f y

Due to the vvelocity of the entering material and air and the spacing of the inlet and outlet in relation to each other, the ne material and channel until the bottom of chute 20 is reached air, wwhich must reverse itself and move through the outlet 21, will have moved below the vane 24 before it can reverse itself, and as the outlet 21v is spaced some distance from the inlet 2I, the

, ne material and air will have reversed itself -before reaching the lower edge of the vane 23.

The fine material and air are reversed some distance below the vanes 2li and 28. v

In operation, there will be a stream of'material and air from the inlet 2l into the chamber B, across its entire width, past the vane 24, and a stream of ne material and air moving out of the chamber B through the outlet 21,'past vane 28. As the air is made to reverse itself, the line material entrained in it will be carried out of the chamber B. The coarse material indistinctly separated inthe rebent portion of chute 2t then moves through the reversing line material and air and into the chute 36, as shown in Fig. 4.

Should the air coming into 'the chamber B through chute 20 be insufcient `to carry outv all the fine material, vanes 25 may be 1 opened to admit additional air from distributing chamber D, so the air will have sullicient force to reverse all the particles Ywhich are sufliciently fine and move them out through the outlet 21.

The wall in which the vanes 25 are located, the

rotor 30, and the wall 31, form an enclosure which` prevents the air and iine material from moving out of the chamber B except through the outlet 21. The pressure in chamber B is arranged to be less than the pressure in chamber D, and the pressure in the outlet 21 is less than in chamber B, due to the action of the fan 62, and the pressure is lcontrolled by valve 5G and the vane 28 in cooperation with wall 31. Valve 5i! can be regulated so that the distributing chamber D, the separating chamber B, and the grinding chamber are below atmospheric pressure in order ythat dust or fumes will be prevented `from escaping. except through the outlet 21. lThe separation can also Abe controlled by regulating the volumeof air passing through Ichamber B by adjusting the vanes 45 or cover 48v or both. In

. up chute 20 be insufficient to force ne particles into outlet 21. While in the construction shown the valve 50 and vane 28 maybe utilized to con-- trol passage of air,v it is tobe understod that it is kin accordance with the invention to entirely contr-ol the passageof air by adjusting the covers 48 and valves 45. The air circulation up chute 20 and through chamber B is effected by the actionof the beaters I2 assisted by the suction of the fan 62, driven by motor M. This suction also indirectly causes air to enter between the vanes 25 when they are opened.

It should be noted that the separation takes place in that part of the chamber where there are no partitions and there are no obstructions within the area where this separation takes place.

The. construction of the casing around the rotor 30, separates the feeder, grinding chamber and the separating chamber into independent units as far as the movement of air is concerned.

The material is discharged from the feeder into the rotor 30 independent of the oversize material which is discharged from the separator and the combined material is discharged into the grinding chamber by the rotor.

The air and line material from chamber B are passed -into a separator 51, the iine material and air being again separated and the coarse material being discharged through the vaned rotor 43a. This allows material to -pass into worm 4|, partially iilling the worm which carries the coarse material toward the mill body until bin connection 40:1: is reached, where the screw conveyor is further filled with a raw material.

The line material and air are drawn out of the separator 51 through duct 6|, by fan 62, thence passes through and into cyclone 53, and is discharged into asuitable container or'sent to storage. The air being relieved of material moves upwardly, part being collected by a hood 53D and returned through the duct 52 to air-distributing chamber D. Excess air that enters through holes 1 in pipes 44 and any leakage that may enter the mill passes eventually into duct 53el and into cloth ilters 50c which trap any material that may be entrained. y

. Vanes 45 and covers 48 are opened until Sullicient air is allowed to pass into grindingchambei' to carry all the material passing between grinding segments I6 and beaters ll2 through chute 2U and into chamber B.

In very ne pulverizing work, the bulk of material to be handled is so large that to separate the nes from so large a mass is impractical in one separation. The first separation in chamber B separates all the very coarse material from the line and the near line. The fines and the near nes are carried up chute 21) by the air (should additional air be needed to carry all the fine material into separators 51, vanes may be opened) through duct 51a, intoseparator 51.

i By partially closing valve 5i) and opening air control 28, the mill proper will be operated below atmospheric pressure. This is an advantage when grinding poisonous material.

It should be noted that the air can enter the grinding chamber only through the pipes 44, and under the iniiuence of the suction effect of the fan $2 the air is drawn through the holes i0 in discs 5 and passes through the vspaces between the beaters when they register lwith the oulet 12a at the bottom of the chute 20r so that air may carry the beaten material upwardly through the said chute 20. As the beaters progress to the air blocked inlet 29 the beaters receive additional material to be ground or beaten and said material is carried between beaters I 2 and tooth-like projections 11 until the location I2a is again reached, whereupon the material and air, as already described, is again projected upwardly into the chute 29. Thus the material is acted on by the beatersr without interference with the rapidly moving air which is only utilized in contact with the ground or beaten material after the beating or grinding action has already taken place. As set forth above, the air and material passing upwardly through the chute 2U and into the separator B travels at a very high velocity.

Referring to Figs. 6, 7, and 8, the generally cylindrical separator 51 comprises an inlet section 5117 and a separator section 51e. The ring or annular disc 58 of generally frusto-conical conliguration forms a baffle or ledge which extends downwardly and inwardly from the inner circumference at the bottom of the cylindrical separator 51.

The ring or annular disc S0 is generally flat and forms a baffle or ledge which extends about the inner circumference of the separator 51 adjacent its top.

The inlet conduit 66 may be of rectangular section and arranged to discharge tangentially into the separator 51 directly'on the ledge 53. The construction shown in the drawings serves to introduce the material and air into the separator l 51 in a thin stream parallel to the vertical inner side of the separator 51 and on the ledge 53.

The lower wall of the inlet duct 51a, reformer 56a and inlet conduit 56 are in a straight line so that entering material will pass to within the separator 51 in a straight line, The reformer 65a serves to reform the stream of air and material for in the construction the duct 51a is circular in cross section and the inlet conduit 66 is rectangular in cross section.

The outlet conduit 51a, leading from the, separator 51, is also of rectangular cross section and is connected to a reformer Gib which in turn is connected to the duct 5l which is of circular cross section. The top section Eilc of the separator 51, in which the outlet conduit G la comprises a cylindrical element closed at its top end, provides a casing `which serves to collect iine material and allow spillingover the edge of the separating ledge 60.

Located at the bottom of the separator 51 is the frusto-conical shaped element 55, the walls of the element 65 tapering downwardly and inwardly and meeting the collar-shaped outlet element 58a. The element 55 is fastened to the separator 51 below the ledge 5.8 and serves to collect the coarse material spilling out oi' the separator 51 and guide it into the revolving vane 59. The rotor 43a is driven by the shaft 43 and sprocket lib which in turn may be driven by any suitable means.

The airl and material may be induced to flow through the separator 51 by the suction fan 62.

The air and material entering the separator 51 in a direction tangential thereto forms a whirling body of air and material, as shown in Fig. 8, which whirling body is supported by the ledge 5B. The material beingheavy in relation to the air is more readily influenced by the action of oentrifugal force created by the rapidly whirling motion and will move tothe outer circumference of thev whirling body adjacent the inner vertical wall of the cylindrical separator l to form a cylindrical mass of whirling material. The inner circumference of the `mass of whirling material will approximately correspond to theinner edges of the ledges 5B and 6Fl as shown in Figure `8.

The incoming material being discharged ron the ledge 58is temporarily supported by 4this ledge and tends to keep from falling over the inner edge of this ledge because of the action oi centrifugal force induced by the rapidly revolving mass, and. the material moves up along the inner walls of the sep-arator El into the section 51e. The coarse material moves to the outermost circumference of the whirling mass and into the separator 5l, the fine material being light and more vreadily acted on by the air,` moves to the inner circumference of the air and material; The

' space between the ledges 58 and G0 being lled with the whirling mass of material, the Vfine material and air will spill over the edge of the ledge 68 into the collecting chamber Bic and the air will carry the iine material out of the collecting chamber through the outlet conduit Sla' The coarse material being held adjacent the in-v ner wall of the separator 51 by the whirling mo'- tionof the revolving mass will tend not' to spill Howover the edge of :the separating ledge Si). ever, the air can hold only a limited quantity of this coarse material under the conditions set forth and the coarse material being relatively heavy and not as readily influenced by the air movement, will move downwardly along the inner wall of the separator 51 and spill over .the ledge 5S whereupon it will be collected by the frustomaterial and air. Disc El) may be held by compression between angles 50a-60a and may be easily changed to regulate the neness of material.

It will be obvious to those skilled in the art that various changes may be made in this device without departing from the spirit of the in-` vention and therefore the invention is not limited to what is shown in the drawings and described in the specication but only as indicated in the appended claims.

What I claim is:

l. The method of pulverizing material comprising: continuously feeding material to be pulverized `to a beating area dened by a path formed on one side by the locus of beating contacts with material being beaten and on the other side by a rebound wall, stripping the material being fed to said beating area of air, maintaining the material in an air stripped condition and siM multaneously beating the material against said wall, permitting the material to rebound from said `wall and applying successive beater blows with such rapidity as to keep the material in continuous motion to and from said wall and withprising: continuously feeding material vto be pullib verized to a beatingarea, continuously stripping the material being VJfed to said beating area of air, maintaining the material in an air Stripped condition and simultaneously beating the material against a continuous stationary wall, permitting the material to rebound from said wall and yapplying successive beating blows with such rapidity as to keep the material in continuous motion to and from the wall and within the beating area,

moving the material along the wall by said beater action, and then utilizing a pulsating current of air toremove the beaten material from the end of the beating areakwhile beating is taking place in said beating area of furthermaterial to be pulverized.

4. The method of pulverizing and separating material comprising: pulverizing material into ne and coarse particles,A utilizingI a current of air to carry the pulverized material, forming the pulverizing material andair into indistinct layers oi air and material, maintaining the formation of indistinct layers of air and material and passing said formation into an unobstructed separating area, reversing the air and fine particles, and passing the ine particles and air through the coarse particles within the unobstructed separating area and then passing the r-ne particles and air out of the unobstructed separating area, passing the coarse particles across the unobstructed separating area and out of the unobstructed separating area. t

5. The lmethod recited in v claim 4, and admittingadditional air lto the unobstructed sepayrating area at one sidevof said indistinct layers andvefecting its passage transversely .thereof to aid in separating the line particles from the K coarse paritcles, the additional air .being added .to

the air and iine particles, and eiecting the passage of lthe additional air out of the unobstructed separating area with the fine particles and air.

6. The method of pulverizing material com prising: `'continuously feeding material to be pulverizedto a beating area, stripping the material being fed to said beating area of air, maintaining the material in an air stripped condition and simultaneously beating the material against a continuous stationary wall, permitting .the material to rebound from said wall and applying successive beating blows with such rapidity as to keep ofy further material to be pulverized, passing the in the beating area, moving the material along said wall by beater action, continuously dischargair current laden with beaten material through a U-shaped path to separate the beaten material and air into indistinct layers, reversing the air and finely beaten material in an unobstructed separating area and separating the coarse material from the air and finely beaten material, discharging the finely beaten material and air from the unobstructed area, discharging the coarse material from the unobstructed area, mixingsaid coarse material with additional material to be pulverized and repeating the steps already cited.

7. The method of pulverizing material comprising: continuously feeding material to be pul verized to a beating area, stripping 'the material being fed to said beating area `o1 air, maintain- -ing the material in an airstripped .condition and rial tov rebound from said wall and applying successive beating blows with such rapidity as to keep the material in continuous motionv to and from the wall and Within the beating area, moving the material along the wall by said beater action, and then utilizing `.a current of air to remove the beaten material from the end of the beating area while beating is taking place in said beating area of further material to be pulverized, separating the coarseparticles from the line particles in the beaten material, mixing the said coarse particles with additional material to be pulverized, and repeating the steps already recited, passing` the iine particles in an air current to a 'second separating area and passing it into the base of a rapidly whirling cylindrical mass, retaining the ne `particles within the whirling cylindrical mass until the most iinely beaten material is separated from the relatively coarse material, spilling the most finely beaten material and air out of the whirling cylindrical mass and passing the most finely lbeaten material and air out of the separating' area, spilling the relatively coarse material out of the inner circumference of the whirling cylindrical mass, passing the coarse material out of the separating area, passing the coarse: material back to the beating area and adding raw material to said coarse material on its way' to the beating area.

il. The method of' pulverizing materia-l com-y prising: continuously feeding materia1 to be pulverized to a beating area, stripping they material being fed to saidbeating area of air', maintaining the material in an air stripped condition and sis multaneously beating the material against a continuous stationary wall, permitting the material torebound from said' wall and applying successive beating blowswith such rapidity as to keep the material in continuous motion to and from the wall and within the beating area, moving the material along the wall by said beater action, and then utilizing a current of ai-r to remove the 'beaten material from the endy of the beating area while beating is taking place insaid beating area of further material to be pulverized, forming the air ycurrent laden with beaten material into indistinct layers, reversing the air and iinely beaten material and air in an unobstructed separating area` and separating the coarse material from the air and nely beaten material, discharging the air and finely beaten material from the unobstructed separating area, discharging the coarse material from the unobstructed separating area, stripping the coarse material of air and returning it to the beating area, passing ythe iinely beaten material and air to a second separating area and forming it' into a rapidly cylindrically whirlingmass, discharging 4the nely beaten material and air into the base of the cylindrically whirling mass, retaining the nely beaten material within the cylindrically whirling mass until the most nely beaten material is separated from the relatively coarse material,v spilling the most finely. beaten material and air from .the cylindrically whirling mass and passing it out of the separating area, spilling the relatively coarse material from lthe inner circumference of the `base of the cylindrically whirling mass, passing the coarse material out of the separating area, passing: the coarse material back to the beating area and adding raw material to said coarse material on its wy to the beating area.

' 9. The method comprising: pulverizing materiaL utilizing a current of air to carry the material,l forming the material and air into a hollow cylindrical whirling mass, confining said whirling' mass at its top and: bottom within annuluses having an outer diameter and an inner diameter, feeding material and air tangentially into the base of said whirling mass directly over the bottorn annulus thereof, effecting the upward passage through said whirling mass of air and fine material, spilling fine material and air upwardly and over the inner circumference oi the upper annulus of said whirling mass, spilling coarse material downwardly over the inner circumference. of the bottom. annulus of said whirling mass.

ADOLPH G. SCHURMAN. 

